Device for treatment with interference currents

ABSTRACT

In interference current therapy, medium-frequency alternating currents are applied by means of electrodes to the body of a patient that is to be treated, the currents differing by a low-frequency difference frequency and interfering with each other in the area under treatment with development of a low frequency beat signal that can effect stimulation. Especially in the case of low frequencies, precise control of the frequency interference current is difficult, and at least one of the medium frequencies must be variable, for adjustment of the low frequency. According to the invention, a common oscillator is provided for both medium frequencies, the essentially higher frequency output of which is divided by a programmable divider into two or more frequencies that differ by the required amount, whereby at least one of the dividers is variable. Various schemes are described for execution of variable frequency division.

This is a division of U.S. application Ser. No. 003,961, filed Jan. 16,1979, now U.S. Pat. No. 4,280,504.

FIELD OF THE INVENTION

The present invention relates to a device for treatment withinterference currents, where two or more frequencies with a slightdifference in frequency interfere with one another in the body that isto be treated.

BACKGROUND OF THE INVENTION

In interference current therapy, an electromedical treatment process isemployed in which, in the area of treatment in question, a stimulus isdeveloped with a low-frequency electric current. The immediate use oflow-frequency alternating current of sufficient current intensity runsinto difficulties however, because the electrical resistance of the areaof treatment is relatively high at low frequencies. Because of this highresistance, there are disagreeable stimulations of the skin in theregion of attachment of the electrodes when using low frequency signals,because of the necessary high voltage, and the intensities ofstimulation deep within the treatment area are inadequate.

Therefore, in interference current therapy, two (or more)medium-frequency currents (with a frequency for example of a fewthousand Hertz) that are independent of each other are applied by meansof electrodes placed on the skin. These medium-frequency currents, whichare respectively ineffective for stimulation, present frequencies thatdiffer by a low-frequency difference. These medium-frequency currentspenetrate into the depth of the area of treatment so as to interferewith each other and thereby produce a low-frequency beat thatcorresponds to the frequency difference. This low beat frequency,because of the physiological properties of the nerves, is stimulating.

In known arrangements of this kind (see German Pat. No. 1,764,672), useis made of two frequencies of about 5000 Hz, where one differs slightlyfrom the other, e.g. 5000 Hz and 5001 Hz. The great difficulty in thisarrangement resides in the fact that this slight difference in frequencyis very difficult to maintain, and also that one of the two frequencieshas to be variable.

SUMMARY OF THE INVENTION

The present invention, therefore, is directed to the problem of creatinga device capable of stable maintenance of the frequency differencewithin a tolerance of 0.01% between the two frequencies, since it isparticularly low differences that are thereapeutically valuable.

According to the invention, this is achieved by the use of a commonoscillator, the output of which is divided from a substantially higherfrequency, by programmable dividers, into two or more frequencies thatdiffer by the required amount, whereby at least one of the dividers isvariable.

According to the invention, the variable division can also be attainedby extending the output period of the frequency dividers by blockingindividual timing pulses, or several such pulses, per output period,whereby the number of blocked pulses will be determined by asupplementary switchable counter or monostable flip-flop which,advantageously, is automatic.

According to the invention, the variation of frequency division can alsooccur through the introduction of additional pulses to the input pulses,as a function of the output pulses, whereby the number of introducedpulses is controlled by a monostable multivibrator with adjustable pulsewidth, advantageously by a supplementary counter, whereby the additionalpulses are phase shifted with respect to the input frequency pulses, sothat they are introduced in between pulses and shorten the duration ofthe output period.

In the device according to the invention, two different frequencies areproduced digitally, by division. Since at least one of the dividers canbe variably programmed, arbitrary differences of frequency can beestablished. The minimum settable difference here depends upon themagnitude of the control frequency. Thus, for example, with a controlfrequency of 50 MHz and a 1/10,000 frequency division (and hence adivided frequency of 5000 Hz) the minimum obtainable frequencydifference is 0.5 Hz. By re-programming the divider, frequencydifferences of 1 Hz, 2 Hz, 4 Hz, 6 Hz etc. can be obtained. Since thesefrequency differences are not only to be stably set but alsoautomatically varied in a specific rhythm, according to the inventionanother frequency divider is connected after the divider output, and theoutput of this additional frequency divider varies the program inputs ofthe variable divider via a switch and a counter device. By thesearrangements, different frequencies in any sequence can automatically bebrought into interference with each other on the body. Therefore, it ispossible not only to have fixed settable frequencies, but also programsthat run automatically with this device.

In frequency dividers in which the pulse-pause ratios are not 1:1, it isadvantageous to connect, thereafter, a pulse shaping stage that producesa symmetrical square wave from the divided pulses.

Since sinusoidal current wave forms are usable in treatment withinterference frequencies, the pulse shaping stage according to theinvention is followed by a curve transforming element which produces asinusoidal curve from the square wave.

This arrangement has a number of advantages as compared with existingdevices.

Thus, the pulse-pause ratio and the pulse frequency of the oscillatorfixes the frequency difference so that no supplementary servicing ortuning operation is necessary. The interference frequency thus does notdepend upon temperature differences, voltage fluctuations or otherfactors, so that a simple and inexpensive construction is produced. Aneconomic advantage is the simple construction from integrated modules,so that it is possible to build it not only economically but also in asmall manageable size. Finally, the digital nature of the device makespossible the use of sensor switches and timing switch devices and fullautomation of the interference current device.

The invention is discussed in more detail with reference to an exampleof embodiment, where further features of the invention are described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of the invention with an appurtenant pulsewaveform;

FIG. 2 shows a device with a programmable frequency divider stage;

FIG. 3 shows a device in which, by blocking individual pulses, thefrequency of one part-frequency can be varied;

FIG. 4 shows a pulse diagram for FIG. 4; and

FIG. 5 shows a device in which, by the introduction of phase-shiftedpulses, the frequency of one part-circuit can be varied.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a common oscillator 1 which produces a pulse train 15 andsupplies the train 15 to a fixed divider 3 and a programmable divider 2.Using a decadic divider, there are produced narrow output pulses 16 thatare converted in pulse shaper stage 4 into a symmetrical square wave 17.Shaping stage 5 converts the square wave 17 into a sinusoidal wave 18.For this purpose, stage 5 may comprise a fundamental wave filter. Outputamplifiers 6 supply the part currents to patient 7 via two separatecircuits so that interference frequencies are generated in the patient'sbody. An additional divider 8 which can be controlled by a switchingdevice 9 sets the fixedly adjusted part-frequency at a frequency of 1 Hzper second and increments the contents of control register 10 of thevariable counter every second, so that the interference frequency isautomatically increased each second.

This automatic device can be cut off by means of switch 19, so thatswitching device 10 can also be arbitrarily varied. This arrangementthus delivers fixed adjustable interference frequencies, but alsointerference phenomena that run automatically, corresponding to theinterference current method in present-day practice.

FIG. 2 shows the circuitry of a programmable divider made of two countermodules 12. Such a frequency divider circuit can change its ratio ofdivision from 1:4096 to 4095:4096. The counter modules 12 arecommercially available switching circuits that require no additionalwiring.

Another possibility for changing the frequency division is shown in FIG.3. Oscillator 1 produces a 25 MHz square wave which is coupled to binaryfrequency divider 2 via the NAND gate 19' until the output of frequencydivider 2 switches from zero to one. At this time, the output of NANDgate 22 goes from one to zero, to disable NAND gate 19' and cut off theinput to frequency divider 2. The transition of the output of frequencydivider 2 to a "one" also sets the reset input of counter 26 from "one"to "zero," via inverter 23, and also sets the input of NAND gate 21 to"one" and thus enables NAND gate 21. Furthermore, because of the zero atthe output of NAND gate 22, NAND gate 20 becomes enabled via inverter 24and thereby controls counter 26 until the output of this counterswitches from zero to one. This has the effect that the NAND gate 21goes from one to zero and NAND gate 22 also switches from zero to oneand blocks NAND gate 20 via inverter 24, so that the output to counter26 is cut off. At the same time, NAND gate 19' is enabled and frequencydivider 2 continues to count pulses. When the output of frequencydivider 2 switches to zero upon recycling at the division count, thereset input of counter 26 will be set to one, via inverter 23, with theeffect that counter 26 will return to zero and the output will remain atzero.

In this way, NAND gate 21 is set at one, and NAND gate 22 is enabled atthe next change from zero to one of frequency divider 2. This frequencydivider circuit has the effect, that, by leaving out a single pulse or aplurality of pulses per output period, the output period can beextended. The number of excluded pulses, and hence the length of theoutput period is controlled by counter 26 whose outputs are selectivelyconnected to NAND gate 21 by a switch 25, depending upon the extensiondesired.

The omission of a pulse at a 25 MHz frequency and with a 1/5000 divisionyields a frequency change on the output of frequency divider 2 of 5000or 4999 Hz. This corresponds to a frequency difference between dividers3 and 2 and hence an interference frequency of 1 Hz.

FIG. 4 shows a pulse diagram in simplified representation, for 1/16division. The same principle obtains for 1/5000 division. Numeral 15represents the train of pulses for which upon switchover of the outputat 29 from zero to one, the next pulse 27 will be blocked. This resultsin the omission as at 28 of a timing period for all following dividerstages and thereby an extension of the output period from 30 to 31,whereby, in this case, the divider ratio will be increased from 16 to17.

In FIG. 5, numeral 1 is a 25 MHz oscillator, the output 35 of which issupplied, on the one hand, to the fixedly set divider 3, and, on theother hand, via diode mixing circuit 40 to variable frequency divider 2,and also to phase changer 32. In phase changer 32 the phase position ofthe input pulses is changed in such a way that pulses 36 shifted viaNAND gate 33 and diode mixing circuit 40 to the input of frequencydivider 2 lie between pulses coming directly from oscillator 1 (curve36).

The output of the variable frequency divider 2 controls monostablemultivibrator 34, whose pulse width 38 is controlled automatically or byswitching. During the pulse duration 38 of the output of multivibrator34, NAND gate 33 is conductive and the diode mixing circuit 40 combinespulses 35 with the phase-shifted pulses 36. Thus, frequency divider 2counts at a 50 MHz rate during pulse 38 and thereby shortens the outputperiod 39. With an introduction of an individual pulse, there is anincrease in frequency at a 1/5000 division, from 5000 and 5005. Fromthis it results that the minimum interference frequency is 0.5 Hz. Acontrol voltage for the automatic control of multivibrator 34 can beobtained by a supplementary frequency divider 8 which is connected tothe output of the fixedly set frequency divider 3. This control voltagevaries the pulse width of the monostable multivibrator 34, e.g. byintegration of the frequency appearing at the output of frequencydivider 8 (not shown in the illustration). By this integration there isformed a delta voltage that can be utilized for pulse width modulationof a monostable multivibrator.

Pursuant to the invention, the control of the monostable multivibratoror of the counter, for variation of frequency, can be effected forparameters other than those described, e.g. delta voltages, square wavevoltages, or waveforms produced by linear structural elements, whereby,in each of the examples, the counting and switchover device can operatevia a "one shot" or monostable multivibrator or another switching unitthat is capable of delivering signals of controllable pulse width.

While I have shown and described several embodiments in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to those skilled in the art and I therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe appended claims.

I claim:
 1. In a device for providing electromedical treatment bycausing a plurality of signals to be applied by electrode means to abody, said signals being of relatively different frequencies tointerfere with one another in the body to be treated, including firstmeans for generating a first relatively high frequency signal in theform of a pulse train; and second means, coupled to said first means andproviding an output to said electrode means, for dividing saidrelatively high frequency signal into a plurality of relatively lowerfrequency signals that differ in frequency by a difference frequency,the improvement comprising:means for controllably varying the divisionof said relatively high frequency signal to one of said relatively lowerfrequency signals, including means for selectively adding one or morepulses to the pulse train of said relatively high frequency signal andcausing the resulting pulse sequence to be controllably divided to alower frequency signal.
 2. The improvement according to claim 1, whereinsaid adding means includes means for shifting the phase of the pulses ofsaid high frequency signal and inserting selected ones of the phaseshifted pulses into said high frequency signal to thereby obtain saidresulting pulse sequence.
 3. The improvement according to claim 2,wherein said adding means includes a monostable multivibrator, theunstable state of which is controllably variable, and a gating circuitenabled by said monostable multivibrator and coupled between the outputof said phase shifting means and a pulse divider circuit.
 4. Theimprovement according to claim 3, further comprising means forconverting said one lower frequency signal to a lower frequencysinusoidal wave.
 5. The improvement according to claim 1, furthercomprising means for converting said one lower frequency signal to asinusoidal waveform.
 6. In a device for providing electromedicaltreatment by causing a plurality of signals to be applied by electrodemeans to a body, said signals being of relatively different frequenciesto interfere with one another in the body to be treated, including firstmeans for generating a first relatively high frequency signal in theform of a pulse train; and second means coupled to said first means andproviding an output to said electrode means for dividing said relativelyhigh frequency signal into a first relatively lower frequency signal;the improvement comprising:third means coupled to said first means fordividing said relatively high frequency signal into a second relativelylower frequency signal which differs in frequency from said firstrelatively lower frequency signal by a frequency difference, includingmeans for adding one or more pulses to the pulse train of saidrelatively high frequency signal to produce a higher frequency signaland means for dividing said higher frequency signal to produce saidsecond relatively lower frequency signal.
 7. The improvement accordingto claim 6, further including means for converting said first and secondrelatively lower frequency pulse signals to a sinusoidal waveform.